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(#) Invalid ID declaration

!!! ERROR: Invalid ID declaration
   This is an error, and is also enforced at build time when
   supported by the build system. For Android this means it will
   run during release builds.

Id
:   `InvalidId`
Summary
:   Invalid ID declaration
Severity
:   Fatal
Category
:   Correctness
Platform
:   Android
Vendor
:   Android Open Source Project
Feedback
:   https://issuetracker.google.com/issues/new?component=192708
Since
:   Initial
Affects
:   Resource files
Editing
:   This check runs on the fly in the IDE editor
Implementation
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-checks/src/main/java/com/android/tools/lint/checks/WrongIdDetector.java)
Tests
:   [Source Code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/WrongIdDetectorTest.kt)
Copyright Year
:   2011

An id definition **must** be of the form `@+id/yourname`. The tools have
not rejected strings of the form `@+foo/bar` in the past, but that was
an error, and could lead to tricky errors because of the way the id
integers are assigned.

If you really want to have different "scopes" for your id's, use
prefixes instead, such as `login_button1` and `login_button2`.

(##) Example

Here is an example of lint warnings produced by this check:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~text
res/layout/invalid_ids.xml:23:Error: ID definitions must be of the form
@+id/name; try using @+id/menu_Reload [InvalidId]
    android:id="@+menu/Reload"
    --------------------------
res/layout/invalid_ids.xml:31:Error: ID definitions must be of the form
@+id/name; try using @+id/_id_foo [InvalidId]
    android:id="@+/id_foo"
    ----------------------
res/layout/invalid_ids.xml:37:Error: ID definitions must be of the form
@+id/name; try using @+id/myid_button5 [InvalidId]
    android:id="@+myid/button5"
    ---------------------------
res/layout/invalid_ids.xml:43:Error: ID definitions must be of the form
@+id/name; try using @+id/string_whatevs [InvalidId]
    android:id="@+string/whatevs"
    -----------------------------
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Here is the source file referenced above:

`res/layout/invalid_ids.xml`:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~xml linenumbers

&lt;!--
  ~ Copyright (C) 2013 The Android Open Source Project
  ~
  ~ Licensed under the Apache License, Version 2.0 (the "License");
  ~ you may not use this file except in compliance with the License.
  ~ You may obtain a copy of the License at
  ~
  ~      http://www.apache.org/licenses/LICENSE-2.0
  ~
  ~ Unless required by applicable law or agreed to in writing, software
  ~ distributed under the License is distributed on an "AS IS" BASIS,
  ~ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  ~ See the License for the specific language governing permissions and
  ~ limitations under the License.
  --&gt;
&lt;RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent" &gt;

    &lt;Button
        android:id="@+menu/Reload"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="Button" /&gt;

    &lt;LinearLayout
        android:id="@+/id_foo"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:orientation="vertical" &gt;

        &lt;Button
            android:id="@+myid/button5"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Button" /&gt;

        &lt;Button
            android:id="@+string/whatevs"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="Button" /&gt;
    &lt;/LinearLayout&gt;

&lt;/RelativeLayout&gt;
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

You can also visit the
[source code](https://cs.android.com/android-studio/platform/tools/base/+/mirror-goog-studio-main:lint/libs/lint-tests/src/test/java/com/android/tools/lint/checks/WrongIdDetectorTest.kt)
for the unit tests for this check to see additional scenarios.

The above example was automatically extracted from the first unit test
found for this lint check, `WrongIdDetector.testInvalidIds1`.
To report a problem with this extracted sample, visit
https://issuetracker.google.com/issues/new?component=192708.

(##) Suppressing

You can suppress false positives using one of the following mechanisms:

* Adding the suppression attribute `tools:ignore="InvalidId"` on the
  problematic XML element (or one of its enclosing elements). You may
  also need to add the following namespace declaration on the root
  element in the XML file if it's not already there:
  `xmlns:tools="http://schemas.android.com/tools"`.

  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;resources xmlns:tools="http://schemas.android.com/tools"&gt;
      ...
      &lt;RelativeLayout id="..." tools:ignore="InvalidId" .../&gt;
    ...
  &lt;/resources&gt;
  ```

* Using a special `lint.xml` file in the source tree which turns off
  the check in that folder and any sub folder. A simple file might look
  like this:
  ```xml
  &lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;lint&gt;
      &lt;issue id="InvalidId" severity="ignore" /&gt;
  &lt;/lint&gt;
  ```
  Instead of `ignore` you can also change the severity here, for
  example from `error` to `warning`. You can find additional
  documentation on how to filter issues by path, regular expression and
  so on
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/lintxml.md.html).

* In Gradle projects, using the DSL syntax to configure lint. For
  example, you can use something like
  ```gradle
  lintOptions {
      disable 'InvalidId'
  }
  ```
  In Android projects this should be nested inside an `android { }`
  block.

* For manual invocations of `lint`, using the `--ignore` flag:
  ```
  $ lint --ignore InvalidId ...`
  ```

* Last, but not least, using baselines, as discussed
  [here](https://googlesamples.github.io/android-custom-lint-rules/usage/baselines.md.html).

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